feat(a11y): Implement keyboard shortcuts and accessibility (Task 13)

- Create AccessibilityContext for global focus management and expanded state
- Add roving tabindex to sidebar with Up/Down/Enter/Home/End navigation
- Focus management: after login, after view change, after item expansion
- Global Escape closes expanded items across all views
- Add scope='col' to SummaryView table headers
- Add focus-after-expand to ConsultationsView
- Update ARIA roles: role='menu', role='menuitem', aria-current

src/contexts/AccessibilityContext.tsx

@@ -0,0 +1,80 @@
+import { createContext, useContext, useState, useCallback, useRef, useEffect, type ReactNode } from 'react'
+
+interface AccessibilityContextValue {
+  expandedItemId: string | null
+  setExpandedItem: (id: string | null) => void
+  requestFocusAfterLogin: () => void
+  focusAfterLoginRef: React.RefObject<HTMLButtonElement | null>
+  focusAfterViewChangeRef: React.RefObject<HTMLHeadingElement | null>
+  requestFocusAfterViewChange: () => void
+}
+
+const AccessibilityContext = createContext<AccessibilityContextValue | null>(null)
+
+export function AccessibilityProvider({ children }: { children: ReactNode }) {
+  const [expandedItemId, setExpandedItemId] = useState<string | null>(null)
+  const focusAfterLoginRef = useRef<HTMLButtonElement | null>(null)
+  const focusAfterViewChangeRef = useRef<HTMLHeadingElement | null>(null)
+  const [shouldFocusAfterLogin, setShouldFocusAfterLogin] = useState(false)
+  const [shouldFocusAfterViewChange, setShouldFocusAfterViewChange] = useState(false)
+
+  const setExpandedItem = useCallback((id: string | null) => {
+    setExpandedItemId(id)
+  }, [])
+
+  const requestFocusAfterLogin = useCallback(() => {
+    setShouldFocusAfterLogin(true)
+  }, [])
+
+  const requestFocusAfterViewChange = useCallback(() => {
+    setShouldFocusAfterViewChange(true)
+  }, [])
+
+  useEffect(() => {
+    if (shouldFocusAfterLogin && focusAfterLoginRef.current) {
+      focusAfterLoginRef.current.focus()
+      setShouldFocusAfterLogin(false)
+    }
+  }, [shouldFocusAfterLogin])
+
+  useEffect(() => {
+    if (shouldFocusAfterViewChange && focusAfterViewChangeRef.current) {
+      focusAfterViewChangeRef.current.focus()
+      setShouldFocusAfterViewChange(false)
+    }
+  }, [shouldFocusAfterViewChange])
+
+  useEffect(() => {
+    const handleKeyDown = (e: KeyboardEvent) => {
+      if (e.key === 'Escape' && expandedItemId) {
+        setExpandedItemId(null)
+      }
+    }
+
+    window.addEventListener('keydown', handleKeyDown)
+    return () => window.removeEventListener('keydown', handleKeyDown)
+  }, [expandedItemId])
+
+  return (
+    <AccessibilityContext.Provider
+      value={{
+        expandedItemId,
+        setExpandedItem,
+        requestFocusAfterLogin,
+        focusAfterLoginRef,
+        focusAfterViewChangeRef,
+        requestFocusAfterViewChange,
+      }}
+    >
+      {children}
+    </AccessibilityContext.Provider>
+  )
+}
+
+export function useAccessibility() {
+  const context = useContext(AccessibilityContext)
+  if (!context) {
+    throw new Error('useAccessibility must be used within AccessibilityProvider')
+  }
+  return context
+}